EP0869313B1

EP0869313B1 - Pulverized fuel combustion burner

Info

Publication number: EP0869313B1
Application number: EP98105045A
Authority: EP
Inventors: Shouzo Kaneko; Tadashi Gengo; Kouichi Sakamoto; Takayoshi Isoda
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1997-03-31
Filing date: 1998-03-19
Publication date: 2001-12-05
Anticipated expiration: 2018-03-19
Also published as: HU9800714D0; EP0869313A1; RO117869B1; EP1054212A2; HU222468B1; ATE210264T1; TW358149B; HUP9800714A3; SK40798A3; EP1054212A3; PL325576A1; PL193795B1; HUP9800714A2; PL191766B1; DK0869313T3; KR100295608B1; SK282933B6; DE69802736T2; CZ293654B6; JPH10274404A

Abstract

A pulverized fuel combustion burner applied to a boiler of a thermal power plant or chemical plant, a furnace of a chemical industry or the like is provided in which, even if the injection direction of the primary air nozzle (1) changes upward or downward, a proper concentration distribution of the mixed flow (7) of the pulverized fuel and the carrier air can be obtained at the exit plane of the furnace side wall and leakage of a portion of the combustion auxiliary air into the furnace is not caused. The pulverized fuel combustion burner comprised a rich/lean flow separator (6) provided at or near the jointed portion between the primary air nozzle (1) and the pulverized fuel supply pipe (3). The rich/lean flow separator is enabled to change its direction in response to or independently of a change in an injection direction of the primary air nozzle. Thus, the rich/lean flow separator follows the change of the direction of the injection of the primary air nozzle and the mixed flow so separated rich and lean can be injected in the same direction as the primary air nozzle without any biasing. <IMAGE>

Description

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a pulverized fuel combustion burner to be applied to a boiler of a thermal power plant or chemical plant, a furnace of a chemical industry or the like.

Related Art

The technique of this kind of the prior art will be described with reference to Fig. 5. Figs. 5(a) to 5(c) are side sections showing a construction of a pulverized fuel combustion burner schematically. Figs. 5(a). 5(b) and 5(c) show the cases, respectively, in which a mixed flow of a pulverized fuel and carrier air is injected horizontally, in which the mixed flow is injected upward, and in which the mixed flow is injected downward.

Reference numeral 1 designates a primary air nozzle, and numeral 2 designates a secondary air nozzle arranged outside of the primary air nozzle 1. Numeral 3 designates a pulverized fuel supply pipe, and numeral 4 designates a combustion auxiliary fuel supply passage which is defined by the pulverized fuel supply pipe 3 and a windbox 5. The pulverized fuel supply pipe 3 communicates at its terminal end with the primary air nozzle 1, and the combustion auxiliary air supply passage 4 communicates with the secondary air nozzle 2.

Reference numeral 10 designates a rich/lean flow separator which is arranged in the pulverized fuel supply pipe 3 so that a mixed flow 7 of the pulverized fuel and the carrier air, as flowing through the pulverized fuel supply pipe 3, may impinge upon the rich/lean flow separator 10 and may be separated by the action of the centrifugal force into a relatively rich flow 8 (as indicated by solid lines) to flow along the outer side and a lean flow 9 (as indicated by broken lines) to flow along the inner side.

Here, reference numeral 12 designates a clearance which is established between the furnace side end portion of the windbox 5 and the windbox side end portion of the secondary air nozzle 2 when the secondary air nozzle 2 is directed upward, as shown in Fig. 5(b), or downward, as shown in Fig. 5(c), by  degrees.

In the ordinary operations, the mixed flow 7 of the pulverized fuel and the carrier air is guided through the pulverized fuel supply pipe 3 into the primary air nozzle 1 so that it is injected into the furnace. On the other hand, the combustion auxiliary air is guided through the combustion auxiliary air supply passage 4 into the secondary air nozzle 2 so that it is injected into the furnace.

In order to satisfy the performances of a low Nox combustion etc. demanded from the combustion aspect, both the relatively rich and

lean flows

8 and 9 of the pulverized fuel, as separated after the mixed flow 7 is separated by the action of the rich/lean flow separator 10, have to be kept with a proper concentration distribution in the furnace side exit plane of the primary air nozzle 1.

Moreover, the combustion auxiliary air has to be injected as wholly as possible through the secondary air nozzle 2 into the furnace thereby to make an effective contribution to the combustion.

Fig. 5(a) shows the state in which the mixed flow 7 and the combustion auxiliary air are injected horizontally into the furnace. In this burner of the prior art, the injection direction of the mixed flow 7 and the combustion auxiliary air into the furnace can be changed upward or downward by directing the primary air nozzle 1 and the secondary air nozzle 2 upward or downward. respectively, as shown in Fig. 5(b) or 5(c).

As a result, the position of the flame to be held in the furnace can be moved upward or downward of the furnace thereby to adjust the gas temperature distribution in the furnace and the gas temperature in the furnace exit plane.

In the burner of the prior art thus far described, the mixed flow 7 of the pulverized fuel and the carrier air can achieve the proper concentration distribution in the furnace side exit plane of the primary air nozzle 1 when it is injected horizontally into the furnace, as shown in Fig. 5(a). When the primary air nozzle 1 is directed upward or downward, respectively, as shown in Fig. 5(b) or 5(c), on the other hand, the relatively rich flow 8 of the pulverized fuel is biased to raise a problem that the mixed flow 7 cannot establish the proper rich/lean distribution in the furnace side exit plane of the primary air nozzle 1 unlike the state shown in Fig. 5(a).

Moreover, the combustion auxiliary air has to pass as wholly as possible through the secondary air nozzle 2. When the secondary air nozzle 2 is directed upward or downward, however, the clearance 12 is established, as shown in Fig. 5(b) or 5(c), between the furnace side end portion of the windbox 5 and the windbox side end portion of the secondary air nozzle 2. As a result, a portion of the combustion auxiliary air bypasses the secondary air nozzle 2 from that clearance 12 and leaks into the furnace thereby to raise a problem that the combustion auxiliary air does not make the effective contribution to the combustion.

A pulverized fuel combustion burner reflecting the prior art is also described in US-A-5 535 686 (Chung).

SUMMARY OF THE INVENTION

The invention contemplates to solve the mentioned problems of the prior art and has an object to provide a pulverized fuel combustion burner which can keep the concentration distribution of the pulverized fuel and can eliminate the leakage of the combustion auxiliary air.

In order to achieve the above-specified object, according to an aspect of the invention, there is provided a pulverized fuel combustion burner according to claim 1.

Specifically, the rich/lean flow separator is arranged at or near the jointed portion between the primary air nozzle and the pulverized fuel supply pipe, and the rich/lean flow separator is enabled to change its direction in response to or independently of the change in the injection direction of the primary air nozzle. Thus, when the primary air nozzle changes its injection direction upward or downward, for example, the rich/lean flow separator follows the direction change so that the mixed air of the rich and lean flows separated thereby is injected without any biasing in accordance with the direction of the primary air nozzle.

According to another aspect of the invention, there is provided a pulverized fuel combustion burner further comprising another rich/lean air separator disposed upstream of the first-named rich/lean flow separator. Specifically, upstream of the rich/lean flow separator disposed at or near the jointed portion between the primary air nozzle and the pulverized fuel supply pipe, there is disposed another rich/lean flow separator. Thus, the rich/lean flow separation is made at first by the rich/lean flow separator positioned upstream and then is further made, by taking over the separation effect, at or near the jointed portion which is near the injection port between the primary air nozzle and the pulverized fuel supply pipe while being followed by the direction changed in accordance with the upward and downward turn of the primary air nozzle.

More specifically, the flow straightener or the straightening plate is disposed at least in any one of the primary air nozzle and the pulverized fuel supply pipe. As a result, the separation result by the rich/lean flow separator is taken over by the flow straightener or the straightening plate so that the rich flow and the lean flow are carried in the separated state and injected through the primary air nozzle into the furnace.

According to a further aspect of the invention, there is provided a pulverized fuel combustion burner further comprising a combustion auxiliary air flow straightener disposed in the windbox for guiding the combustion auxiliary air into an entrance of the secondary air nozzle. Specifically, the leakage of the combustion auxiliary air at the entrance of the secondary air nozzle can be drastically prevented not only by devising the primary air nozzle for guiding the mixed flow of the pulverized fuel and the carrier air preferably but also by guiding the combustion auxiliary air to the entrance of the secondary air nozzle by the combustion auxiliary air flow straightener disposed in the windbox.

According to a further aspect of the invention, there is provided a pulverized fuel combustion burner, wherein the primary air nozzle is disposed at a corner portion of the side wall of the furnace. Specifically, the burner is devised to separate the mixed flow of the pulverized fuel and the carrier air into the rich flow and the lean flow by the pulverized fuel supply pipe and the primary air nozzle and to keep the separation effect, and is arranged at the corner portion of the furnace side wall so that the preferable injection may be effected from the corner portion into the furnace.

According to a further aspect of the invention, there is provided a pulverized fuel combustion burner, wherein the windbox comprises a plurality of unit windboxes, each having a square front section and each having at least one pulverized fuel supply pipe and one combustion auxiliary air supply passage, said unit windboxes being arranged in a separated or jointed relation between each other, and the unit windbox has an upward and downward directional length of one and a half(1.5) times or less of its lateral directional length.

Specifically, the unit windbox is constructed by housing the primary air nozzle, which is devised to separate the mixed flow of the pulverized fuel and the carrier air by the pulverized fuel supply pipe and the primary air nozzle and to keep the separation effect, and the secondary air nozzle which prevents the leakage of the combustion auxiliary air at its entrance, and the unit windbox has an upward and downward directional length of one and a half(1.5) times or less of its lateral directional length, thereby to make the entire construction compact without lowering the performance.

BRIEF DESCRIPTION OF THE DRAWINGS

Of Figs. 1(a), 1(b) and 1(c), which do not fall within the scope of the present invention, schematically showing a pulverized fuel combustion burner: Fig. 1(a) is an explanatory diagram showing the case in which a mixed flow of a pulverized fuel and carrier air is injected horizontally; Fig. 1(b) is an explanatory diagram showing the case in which the mixed flow is injected upward; and Fig. 1(c) is an explanatory diagram showing the case in which the mixed flow is injected downward;

Of Figs. 2(a), 2(b) and 2(c), which do not fall within the scope of the present invention, schematically showing a pulverized fuel combustion burner: Fig. 2(a) is an explanatory diagram showing the case in which a mixed flow of a pulverized fuel and carrier air is injected horizontally: Fig. 2(b) is an explanatory diagram showing the case in which the mixed flow is injected upward; and Fig. 2(c) is an explanatory diagram showing the case in which the mixed flow is injected downward;

Of Figs. 3(a), 3(b) and 3(c) schematically showing a pulverized fuel combustion burner according to a first embodiment of the Invention: Fig. 3(a) is an explanatory diagram showing the case in which a mixed flow of a pulverized fuel and carrier air is injected horizontally; Fig. 3(b) is an explanatory diagram showing the case in which the mixed flow is injected upward; and Fig. 3(c) is an explanatory diagram showing the case in which the mixed flow is injected downward;

Of Figs. 4(a), 4(b) and 4(c) schematically showing a pulverized fuel combustion burner according to a second embodiment of the Invention: Fig. 4(a) is an explanatory diagram showing the case in which a mixed flow of a pulverized fuel and carrier air is injected horizontally; Fig. 4(b) is an explanatory diagram showing the case in which the mixed flow is injected upward; and Fig. 4(c) is an explanatory diagram showing the case in which the mixed flow is injected downward; and

Of Figs. 5(a), 5(b) and 5(c) schematically showing a pulverized fuel combustion burner of the prior art: Fig. 5(a) is an explanatory diagram showing the case in which a mixed flow of a pulverized fuel and carrier air is injected horizontally; Fig. 5(b) is an explanatory diagram showing the case in which the mixed flow is injected upward; and Fig. 5(c) is an explanatory diagram showing the case in which the mixed flow is injected downward.

Of Fig. 6 is an explanatory view showing an example of arrangement of a pulverized fuel combustion burner in a furnace with respect to each of the embodiments according to the present invention.

Of Fig. 7 is an explanatory view showing an outline of a unit windbox constructed by the pulverized fuel combustion burner with respect to each of the embodiments according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figs. 1(a) to 1(c) are side sections showing a construction of a pulverized fuel combustion burner schematically. Figs. 1(a), 1(b) and 1(c) show the cases, respectively, in which a mixed flow of a pulverized fuel and carrier air is injected horizontally, in which the mixed flow is injected upward, and in which the mixed flow is injected downward. Here, the portions identical to those of the prior art are designated by the common reference numerals, and their overlapped description will be omitted.

At the jointed portion between the primary air nozzle 1 and the pulverized fuel supply pipe 3, there is arranged the rich/lean flow separator 6 which is connected to the primary air nozzle 1 by a suitable joint mechanism so that its direction may be changed as the primary air nozzle 1 changes its injection direction.

Incidentally, the rich/lean flow separator 6 can also be given a structure separate from the primary air nozzle 1 and can act by itself so that it can detect the motion of the primary air nozzle 1 to change its direction according to the motion detected.

Reference numeral 11 designates a dispersing device which is arranged at the outer side in the bent portion where the pulverized fuel supply pipe 3 is curved upstream, so that a rich mixture flow having a tendency to diverge by the centrifugal force may impinge upon the dispersing device and may be homogeneously dispersed in the pulverized fuel supply pipe 3.

The rich/lean flow separator 6 is constructed to follow the change in the direction of the primary air nozzle 1, as described above. While the primary air nozzle 1 is directed horizontally, as shown in Fig. 1(a), the rich/lean flow separator 6 is also directed horizontally. When the primary air nozzle 1 is directed upward, as shown in Fig. 1(b), the rich/lean flow separator 6 is accordingly directed upward. When the primary air nozzle is directed downward, as shown in Fig. 1(c), the rich/lean flow separator 6 is accordingly directed downward. Thus, the rich/lean flow separator 6 acts to introduce the flow of the mixed flow 7 in the same direction as that of the injection into the furnace by the primary air nozzle 1.

Thus, both the rich flow 8 and the lean flow 9 of the pulverized fuel to be prepared by the rich/lean flow separator 6 can establish a flow which maintains a concentration distribution equivalent to that of the case in which the mixed flow 7 is being injected horizontally. Even if the direction for the primary air nozzle 1 to inject the mixed flow 7 changes from the horizontal to upward and downward directions, the concentration distribution, as demanded from the combustion efficiency of the fuel, can be kept and retained without establishing any biased flow in the exit plane of the primary air nozzle 1.

Here, the primary air nozzle (burner nozzle) thus constructed is arranged at each corner portion of the furnace side wall (furnace wall), as shown in Fig. 6 schematically, so that the mixed flow of the pulverized fuel, as separated rich and lean, and the carrier air may be efficiently injected from the corner portion into the furnace.

Also, as shown in Fig. 7, a unit windbox having a square front section is made of at least one pulverized fuel supply pipe and one combustion auxiliary air supply pipe , and a plurality of these unit windboxes are arranged either separately or by jointing them. This construction is made compact as a whole by making the upward and downward directional length of the unit windbox one and a half(1.5) times or less of the lateral directional length of the windbox. It is to be noted that, in Fig. 7, a coal burner which is constructed by the pulverized fuel supply pipe, the combustion auxiliary air supply passage, etd. and an oil burner are shown, but when no oil fuel is supplied, the oil burner may be used as an air port for supplying the auxiliary air.

Like Figs. 1(a) to 1(c), Figs. 2(a) to 2(c) are side sections showing a construction of a pulverized fuel combustion burner schematically. Figs. 2(a), 2(b) and 2(c) show the cases, respectively, in which a mixed flow of a pulverized fuel and carrier air is injected horizontally, in which the mixed flow is injected upward, and in which the mixed flow is injected downward. Here, the portions identical to those of the prior art or the combustor of Figs. 1(a) to 1(c) are designated by the common reference numerals, and their overlapped description will be omitted.

Another rich/lean flow separator 10 is arranged upstream of the rich/lean flow separator 6 which is disposed at the jointed portion between the primary air nozzle 1 and the pulverized fuel supply pipe 3.

Of these rich/

lean flow separators

6 and 10, the downstream one 6, as disposed at the jointed portion between the primary air nozzle 1 and the pulverized fuel supply pipe 3, is of such a variable type as to act according to the action of the primary air nozzle 1, as in the combustor of Figs. 1(a) to 1(c), to change the flow direction so that the relatively rich and

lean flows

8 and 9 may be established in the same direction in which the pulverized fuel is injected into the furnace. On the other hand, the other rich/lean flow separator 10, as arranged upstream, may be either of a fixed type or a variable type in which it is not especially restrained by the action of the primary air nozzle 1.

The mixed flow 7 is separated at first into the rich and lean flows by the upstream rich/lean flow separator 10 and is then guided into the downstream rich/lean flow separator 6 and the primary air nozzle 1. Next, as in the combustor of Figs. 1(a) to 1(c), the downstream rich/lean flow separator 6 is constructed to follow the change in the direction of the primary air nozzle 1, as described above. While the primary air nozzle 1 is directed horizontally, as shown in Fig. 2(a), the rich/lean flow separator 6 is also directed horizontally. When the primary air nozzle 1 is directed upward, as shown in Fig. 2(b), the rich/lean flow separator 6 is accordingly directed upward. When the primary air nozzle is directed downward, as shown in Fig. 2(c), the rich/lean flow separator 6 is accordingly directed downward. Thus, the rich/lean flow separator 6 acts to introduce the flow of the mixed flow 7 in the same direction as that of the injection into the furnace by the primary air nozzle 1.

By this action, the pulverized fuel, as prepared by the rich/

lean flow separators

6 and 10, is enabled to establish the flows keeping a concentration distribution equivalent to that of the case in which both the rich flow 8 and the lean flow 9 are injected horizontally, as shown in Fig. 2(a).

Even if the direction for the primary air nozzle 1 to inject the mixed flow 7 changes from the horizontal to upward and downward directions, with the additional action of the rich/lean flow separator 10, the concentration distribution, as demanded from the combustion efficiency of the fuel, can be kept and retained in the exit plane of the primary air nozzle 1.

Further, an embodiment of the present invention will be described with reference to Figs. 3(a) to 3(c). Figs. 3(a) to 3(c) are side sections showing a construction of a pulverized fuel combustion burner schematically. Figs. 3(a). 3(b) and 3(c) show the cases. respectively, in which a mixed flow of a pulverized fuel and carrier air is injected horizontally, in which the mixed flow is injected upward, and in which the mixed flow is injected downward. Here, the portions identical to those of the prior art or the first and second embodiments are designated by the common reference numerals, and their overlapped description will be omitted.

This embodiment is provided with a first straightening plate 13 which is disposed in the primary air nozzle 1 and changes its direction in accordance with the change in the direction of the primary air nozzle 1, and a second straightening plate 14 which is disposed in the pulverized fuel supply pipe 3 downstream of the rich/lean flow separator 10.

In this embodiment, the mixed flow 7 of the pulverized fuel and the carrier air is injected horizontally from the primary air nozzle 1, as shown in Fig. 3(a), and the primary air nozzle 1 changes its direction to inject the mixed flow 7 upward or downward, as shown in Fig. 3(b) or 3(c).

Before this injection, this mixed flow 7 is separated into rich and lean flows by the rich/lean flow separator 10 arranged at the upstream side, and is then introduced into the primary air nozzle 1.

First of all, as shown in Fig. 3(a), the second straightening plate 14 in the pulverized fuel supply pipe 3 acts to keep the concentration distribution, as determined by the rich flow 8 and the lean flow 9 of the pulverized fuel, at a stage before the rich flow 8 and the lean flow 9 reach the primary air nozzle 1. The first straightening plate 13 in the primary air nozzle 1 acts to direct the rich flow 8 of the pulverized fuel toward the inner face of the primary air nozzle 1.

When the primary air nozzle 1 is directed upward or downward by  degrees, as shown in Figs. 3(b) or 3(c), too, the pulverized fuel is enabled to keep the concentration distribution of the rich flow 8 and the lean flow 9, as established by the rich/lean flow separator 10, by the straightening actions of the second straightening plate 14 in the pulverized fuel supply pipe 3 and the first straightening plate 13 in the primary air nozzle 1.

By the actions of these first and

second straightening plates

13 and 14. the rich flow 8 and the lean flow 9 of the pulverized fuel are enabled to establish the flows which keep the concentration distribution equivalent to that of the case in which the mixed flow 7 is injected horizontally, as shown in Fig. 3(a). Even if the direction for the primary air nozzle 1 to inject the mixed flow 7 changes from the horizontal to upward and downward directions, with the additional action of the rich/lean flow separator 10, the concentration distribution, as demanded from the combustion efficiency of the fuel, can be kept and retained in the exit plane of the primary air nozzle 1.

Further, a second embodiment of the present invention will be described with reference to Figs. 4(a) to 4(c). Like the first embodiment, Figs. 4(a) to 4(c) are side sections showing a construction of a pulverized fuel combustion burner schematically. Figs. 4(a), 4(b) and 4(c) show the cases, respectively, in which a mixed flow of a pulverized fuel and carrier air is injected horizontally, in which the mixed flow is injected upward, and in which the mixed flow is injected downward. Here, the portions identical to those of the prior art or the first embodiment are designated by the common reference numerals, and their overlapped description will be omitted.

In this embodiment, there is disposed in the combustion auxiliary air supply passage 4, a combustion auxiliary air flow straightener 15 which is arranged inside of the windbox 5 and in the vicinity of the jointed portion between the secondary air nozzle 2 and the combustion auxiliary air supply passage 4. Here, reference numeral 16 designates the combustion auxiliary air to be injected from the combustion auxiliary air supply passage 4 through the secondary air nozzle 2 into the furnace. Numeral 17 designates the combustion auxiliary air which bypasses the secondary air nozzle 2 from the combustion auxiliary air supply passage 4 and leaks around the secondary air nozzle 2 into the furnace.

In this embodiment, the mixed flow 7 of the pulverized fuel and the carrier air is dispersed by the dispersing device 11 and separated into the rich and lean flows by the rich/lean flow separator 10 until it is guided into the primary air nozzle 1.

The combustion auxiliary air flow straightener 15 acts to change the flow direction of the combustion auxiliary air so positively that the combustion auxiliary air having passed the vicinities of the upper inner wall face and the lower inner wall face of the combustion auxiliary air supply passage 4 may pass through the inside of the secondary air nozzle 2.

As shown in Figs. 4(b) and 4(c), too, the combustion auxiliary air flow straightener 15 acts to change the flow direction of the combustion auxiliary air so positively that the combustion auxiliary air having passed the vicinities of the upper inner wall face and the lower inner wall face of the combustion auxiliary air supply passage 4 may pass through the inside of the secondary air nozzle 2.

By the action of this combustion auxiliary air flow straightener 15, almost all the combustion auxiliary air can be the combustion auxiliary air 16 to be injected into the furnace through the secondary air nozzle 2, while minimizing the amount of the air 17 which might otherwise bypasses the secondary air nozzle 2 and leaks into the furnace.

Although the invention has been described in connection with the shown embodiments, it should not be limited thereto but can naturally be variously modified in its specific structure within the scope of the appended claims.

The pulverized fuel combustion burner according to the invention is constructed to comprise a plurality of air nozzles arranged on a side wall of a furnace for injecting a mixed flow of a pulverized fuel and carrier air to establish a flame, said air nozzles including a primary air nozzle having a variable direction to inject said mixed flow into the furnace, a secondary air nozzle for feeding combustion auxiliary air to around said primary air nozzle, a windbox comprising a pulverized fuel supply pipe for feeding said mixed flow to said primary air nozzle, wherein said pulverized fuel supply pipe extends through said windbox such that a combustion auxiliary air supply passage is formed around said pulverized fuel supply pipe, wherein a rich/lean flow separator is disposed in said pulverized fuel supply pipe and wherein a flow straightener or a straightening plate disposed at least in any one of said primary air nozzle and said pulverized fuel supply pipe downstream of said rich/lean flow separator for maintaining a concentration distribution, as established by said rich/lean flow separator, to an exit of said primary air nozzle. As a result, the flow straightener or straightening plate takes the separation result by the rich/lean separator so that the mixed flow of the pulverized fuel. and the carrier air can be conveyed while keeping separate in the rich flow and the lean flow and injected for the preferable combustion from the primary air nozzle into the furnace, thereby to enhance the reliability as the pulverized fuel combustion burner.

The pulverized fuel combustion burner according to the invention of Claim 2 is constructed to further comprise a combustion auxiliary air flow straightener disposed in said windbox for guiding said combustion auxiliary air into an entrance of said secondary air nozzle. As a result, the mixed flow of the pulverized fuel and the carrier air can be injected in a preferable situation from the primary air nozzle, and the combustion auxiliary air can be guided in a preferable state from the outer side into the entrance of the secondary air nozzle by the combustion auxiliary air flow straightener disposed in the windbox, thereby to prevent the leakage of the combustion auxiliary air drastically at the entrance of the secondary air nozzle.

The pulverized fuel combustion burner according to the invention of Claim 3 is constructed such that said primary air nozzle is disposed at a corner portion of the side wall of the furnace. As a result, the burner is devised to separate the mixed flow of the pulverized fuel and the carrier air into the rich flow and the lean flow by the pulverized fuel supply pipe and the primary air nozzle and to keep the separation effect, and is arranged at the corner portion of the furnace side wall so that the preferable injection can be effected from the corner portion into the furnace, thereby to retain the proper combustion.

The pulverized fuel combustion burner according to Claim 4 is constructed such that said windbox comprises a plurality of unit windboxes each having a square front section and each having at least one pulverized fuel supply pipe and one combustion auxiliary air supply passage, said unit windboxes being arranged in a separated or jointed relation between each other, and each said unit windbox has an upward and downward directional length of one and a half(1.5) times or less of its lateral directional length. As a result, the unit windbox is constructed by housing the primary air nozzle, which is devised to separate the mixed flow of the pulverized fuel and the carrier air by the pulverized fuel supply pipe and the primary air nozzle and to keep the separation effect, and the secondary air nozzle which prevents the leakage of the combustion auxiliary air at its entrance, and the unit windbox has an upward and downward directional length of one and a half(1.5) times or less of its lateral directional length, so that the entire construction can be made compact without lowering the performance.

Claims

A pulverized fuel combustion burner comprising a plurality of air nozzles arranged on a side wall of a furnace for injecting a mixed flow (7) of a pulverized fuel and carrier air to establish a flame,
said air nozzles including:

a primary air nozzle (1) having a variable direction to inject said mixed flow (7) into the furnace,

a secondary air nozzle (2) for feeding combustion auxiliary air to around said primary air nozzle (1), and

a windbox (5) comprising a pulverized fuel supply pipe (3) for feeding said mixed flow (7) to said primary air nozzle (1), wherein said pulverized fuel supply pipe (3) extends through said windbox (5) such that a combustion auxiliary air supply passage (4) is formed around said pulverized fuel supply pipe (3),

wherein a rich/lean flow separator (10) is disposed in said pulverized fuel supply pipe (3), and

a flow straightener (15) or a straightening plate (13,14) is disposed at least in any one of said primary air nozzle (1) and said pulverized fuel supply pipe (3) downstream of said rich/lean flow separator (10) for maintaining a concentration distribution as established by said rich/lean flow separator (10) to an exit of said primary air nozzle (1).
A pulverized fuel combustion burner as set forth in claim 1, wherein a combustion auxiliary air flow straightener (15) is disposed in said windbox (5) for guiding said combustion auxiliary air (16) into an entrance of said secondary air nozzle (2).
A pulverized fuel combustion burner as set forth in claim 1 or 2, wherein said primary air nozzle (1) is disposed at a corner portion of the side wall of the furnace.
A pulverized fuel combustion burner as set forth in any one of claims 1 to 3, wherein said windbox (5) comprises a plurality of unit windboxes, each having a square front section and each having at least one said pulverized fuel supply pipe (3) and one said combustion auxiliary air supply passage (4), said unit windboxes being arranged in a separated or jointed relation between each other, and each said unit windbox has an upward and downward directional length (h) of one and a half (1.5 times) or less of its lateral directional length (w).